Maya Rudolph
Credit: Jemal Countess/Getty Images

It's a milestone for Maya Rudolph! The Bridesmaids comedienne, who first charmed audiences on Saturday Night Live before switching to primetime with Up All Night, celebrates her 40th birthday today. And she's not the only big name who entered her fourth decade in 2012. Click through to see all the stars turning 40 this year, including Jennifer Garner, Cameron Diaz, and more!